1. Field of the Invention
The present invention relates to a composite substrate suitably used for a semiconductor device, and a composite base suitably used for that composite substrate.
2. Description of the Background Art
Composite substrates in which a semiconductor crystal layer is attached to a different composition base having a chemical composition different from that of the semiconductor crystal layer have been proposed to efficiently manufacture semiconductor devices with excellent properties.
For example, Japanese Patent Laying-Open No. 2003-165798 discloses a method of manufacturing a gallium nitride single crystal substrate by attaching a single crystal sapphire substrate to a base to fabricate a sapphire composite substrate and epitaxially growing a gallium nitride single crystal on a sapphire surface of the sapphire composite substrate.